scholarly journals Observations and experiments on regeneration in Hydra viridis

1901 ◽  
Vol 13 (1-2) ◽  
pp. 135-178 ◽  
Author(s):  
Helen Bean King
Keyword(s):  
Hydra Viridis

Ultrastructural Changes of the Symbiotic Chlorella-Like Alga Isolated from Hydra Viridis

1982 ◽  
Vol 40 ◽  
pp. 320-321
Author(s):  
K.W. Lee ◽  
R.H. Meints ◽  
D. Kuczmarski ◽  
J.L. Van Etten
Keyword(s):  
Time Course ◽  
Reciprocal Cross ◽  
Ultrastructural Level ◽  
Ultrastructural Changes ◽  
Symbiotic Relationship ◽  
Cell Recognition ◽  
Green Hydra ◽  
Different Strains ◽  
Hydra Viridis

The physiological, biochemical, and ultrastructural aspects of the symbiotic relationship between the Chlorella-like algae and the hydra have been intensively investigated. Reciprocal cross-transfer of the Chlorellalike algae between different strains of green hydra provide a system for the study of cell recognition. However, our attempts to culture the algae free of the host hydra of the Florida strain, Hydra viridis, have been consistently unsuccessful. We were, therefore, prompted to examine the isolated algae at the ultrastructural level on a time course.

Algal endosymbiosis in brown hydra: host/symbiont specificity

1986 ◽  
Vol 86 (1) ◽  
pp. 273-286 ◽  
Author(s):  
M. Rahat ◽  
V. Reich
Keyword(s):  
Ecological Factors ◽  
Vacuolar Membrane ◽  
Physiological Strain ◽  
Free Living ◽  
Daughter Cells ◽  
Green Hydra ◽  
Endodermal Cells ◽  
Hydra Viridis ◽  
Algal Distribution

Host/symbiont specificity has been investigated in non-symbiotic and aposymbiotic brown and green hydra infected with various free-living and symbiotic species and strains of Chlorella and Chlorococcum. Morphology and ultrastructure of the symbioses obtained have been compared. Aposymbiotic Swiss Hydra viridis and Japanese H. magnipapillata served as controls. In two strains of H. attenuata stable hereditary symbioses were obtained with Chlorococcum isolated from H. magnipapillata. In one strain of H. vulgaris, in H. oligactis and in aposymbiotic H. viridis chlorococci persisted for more than a week. Eight species of free-living Chlorococcum, 10 symbiotic and 10 free-living strains of Chlorella disappeared from the brown hydra within 1–2 days. In H. magnipapillata there was a graded distribution of chlorococci along the polyps. In hypostomal cells there were greater than 30 algae/cell while in endodermal cells of the mid-section or peduncle less than 10 algae/cell were found. In H. attenuata the algal distribution was irregular, there were up to five chlorocci/cell, and up to 20 cells/hydra hosted algae. In the dark most cells of Chlorococcum disappeared from H. magnipapillata and aposymbiotic hydra were obtained. Chlorococcum is thus an obligate phototroph, and host-dependent heterotrophy is not required for the preservation of a symbiosis. The few chlorococci that survived in the dark seem to belong to a less-demanding physiological strain. In variance with known Chlorella/H. viridis endosymbioses the chlorococci in H. magnipapillata and H. attenuata were tightly enveloped in the vacuolar membrane of the hosting cells with no visible perialgal space. Chlorococcum reproduced in these vacuoles and up to eight daughter cells were found within the same vacuole. We suggest that the graded or scant distribution of chlorococci in the various brown hydra, their inability to live in H. viridis and the inability of the various chlorellae to live in brown hydra are the result of differences in nutrients available to the algae in the respective hosting cells. We conclude that host/symbiont specificity and the various forms of interrelations we show in green and brown hydra with chlorococci and chlorellae are based on nutritional-ecological factors. These interrelations demonstrate successive stages in the evolution of stable obligatoric symbioses from chance encounters of preadapted potential cosymbionts.

Hydra viridis: Inhibition by the Basal Disk of Basal Disk Differentiation

Science ◽  
1968 ◽  
Vol 159 (3820) ◽  
pp. 1246-1247 ◽  
Author(s):  
H. K. MacWilliams ◽  
F. C. Kafatos
Keyword(s):  
Basal Disk ◽  
Hydra Viridis

A histological and ultrastructural study of dedifferentiation and redifferentiation of digestive and gland cells in Hydra viridis

1966 ◽  
Vol 14 (2) ◽  
pp. 307-329 ◽  
Author(s):  
Lowell E. Davis ◽  
Allison L. Burnett ◽  
Julian F. Haynes ◽  
Virgil R. Mumaw
Keyword(s):  
Ultrastructural Study ◽  
Gland Cells ◽  
Hydra Viridis

The ultrastructure of the zymogen cells in Hydra viridis

1969 ◽  
Vol 100 (2) ◽  
pp. 316-324 ◽  
Author(s):  
Julian F. Haynes ◽  
Lowell E. Davis
Keyword(s):  
Hydra Viridis

Maltose excretion by the symbiotic algae of Hydra viridis

1969 ◽  
Vol 173 (1033) ◽  
pp. 557-576 ◽  
Keyword(s):  
Cell Surface ◽  
Soluble Sugar ◽  
Direct Proof ◽  
Insoluble Fraction ◽  
Animal Tissue ◽  
Fixed Carbon ◽  
Short Term ◽  
Symbiotic Algae ◽  
Hydra Viridis ◽  
External Ph

The sym biotic algae (zoochlorellae) of Hydra viridis live inside the gastrodermal cells. When isolated into pure suspension free of animal tissue, zoochlorellae liberate maltose to the medium during photosynthesis. Maltose synthesis and excretion are very sensitive to external pH. At pH 4.0, about 40 to 50 % of the carbon fixed in photosynthesis may be released from the cells as maltose, and a further 4 to 6 % as other compounds (including alanine, glycollie acid, glucose, and an oligosaccharide provisionally identified as maltotriose). As the pH rises, excretion progressively diminishes, and at pH 7.0, only about 1% of the photo synthetically fixed carbon is excreted, about half as maltose. Only traces of maltose are ever found within the cells, and sucrose is always the predominant intracellular soluble sugar. When cells previously labelled with 14 C at pH 7.0 are transferred to non-radioactive media in the dark at pH 4.0, they immediately begin to synthesize and excrete [ 14 C ]maltose; the increase of [ 14 C]maltose is closely correlated with a decrease of 14 C-labelled hexose monophosphates and is not accompanied by any loss of 14 C from the insoluble fraction. This suggests that maltose is synthesized from hexose monophosphates by a process which is not directly light dependent. In short-term photosynthesis experiments at pH 4.0, fixed 14 C appears in sucrose within 20s, but none appears in maltose until 60 s. This, together with the near absence of intracellular maltose and the marked sensitivity of maltose synthesis to external pH, suggests that the mechanism of synthesis is at or near the cell surface. The experimental results were consistent with the hypothesis that maltose synthesis is UDPG -dependent, but direct proof of this was n o t obtained. Although excretion of photosynthetically fixed 14 C at pH 4.0 diminishes in the presence of external maltose, it could still continue at an appreciable rate when the external maltose concentration was as high as 10% (w/v). In 10% maltose media, some of the excreted 14 C was still in maltose, but most was in compounds provisionally identified as maltotriose and maltotetrose, suggesting that a mechanism for transglycosylation may exist on the surface of the cells. Unlike symbiotic zooxanthellae and lichen algae, Hydra zoochlorellae show no signs of losing their ability of excreting carbohydrate during the first 24 h after isolation from the symbiosis. In the case of Hydra , it is suggested that the host might be able to control maltose excretion from its zoochlorellae by variations in the intracellular pH of the gastrodermal cells, but evidence for such changes is still lacking.

The effect of glycerol on the Chlorella symbiosis in Hydra viridis

Hydrobiologia ◽  
1981 ◽  
Vol 85 (1) ◽  
pp. 59-65 ◽  
Author(s):  
Clive R. Wilkinson ◽  
David C. Smith
Keyword(s):  
Hydra Viridis
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